Low permeability side curtain airbag cushions having extremely low coating levels

ABSTRACT

Coated inflatable fabrics, more particularly airbags to which very low add-on amounts of coating have been applied, are provided which exhibit extremely low air permeabilities. The inventive fabrics are primarily for use in automotive restraint cushions which require low permeability characteristics (such as side curtain airbags). Traditionally, heavy, and thus expensive, coatings of compounds such as neoprene, silicones and the like, have been utilized to provide such required low permeability. The inventive fabric utilizes an inexpensive, very thin coating to provide such necessary low permeability levels. Thus, the inventive coated airbag possesses a coating of at most 3.0 ounces per square yard, most preferably about 0.8 ounces per square yard, and exhibits a leak-down time (a measurement of the time required for the entire amount of gas introduced within the airbag at peak pressure during inflation to escape the airbag at 10 psi) of at least 7 seconds. All coatings, in particular elastomeric, non-silicon coatings, and coated airbags, meeting these criteria are intended to reside within the scope of this invention.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.09/501,467, filed Feb. 9, 2000, which is a continuation-in-part of Ser.No. 09/350,620, filed on Jul. 9, 1999, now U.S. Pat. No. 6,177,366,which is a continuation-in-part of Ser. No. 09/335,257, filed on Jun.17, 1999, now U.S. Pat. No. 6,177,365; this application is also acontinuation-in-part of application Ser. No. 09/406,264, filed on Sep.24, 1999, now U.S. Pat. No. 6,220,309. These parent applications areherein entirely incorporated by reference.

FIELD OF THE INVENTION

All U.S. Patents cited herein are entirely incorporated by reference.

This invention relates generally to coated inflatable fabrics and moreparticularly concerns airbag cushions to which very low add-on amountsof coating have been applied and which exhibit extremely low airpermeability. The inventive inflatable fabrics are primarily for use inautomotive restraint cushions that require low permeabilitycharacteristics (such as side curtain airbags). Traditionally, heavy,and thus expensive, coatings of compounds such as neoprene, siliconesand the like, have been utilized to provide such required lowpermeability. The inventive fabric utilizes an inexpensive, very thincoating to provide such necessarily low permeability levels. Thus, theinventive coated inflatable airbag possesses a coating comprising anelastomeric material (or materials) in contact with the target fabricwherein the elastomeric material possesses a tensile strength of atleast 2,000 psi and an elongation at break of at least 180%. The coatingis then applied to the airbag surface in an amount of at most 3.0 ouncesper square yard (and preferably forms a film). The inventive airbagexhibits a characteristic leak-down time (defined as the ratio ofinflated bag volume to bag volumetric leakage rate at 10 psi) of atleast 5 seconds after inflation. The resultant airbag cushions,particularly low permeability cushions exhibiting very low rolledpacking volumes, are intended to reside within the scope of thisinvention.

BACKGROUND OF THE PRIOR ART

Airbags for motor vehicles are known and have been used for asubstantial period of time. A typical construction material for airbagshas been a polyester or nylon fabric, coated with an elastomer such asneoprene, or silicone. The fabric used in such bags is typically a wovenfabric formed from synthetic yarn by weaving practices that are wellknown in the art.

The coated material has found acceptance because it acts as animpermeable barrier to the inflation medium. This inflation medium isgenerally a nitrogen or helium gas generated from a gas generator orinflator. Such gas is conveyed into the cushion at a relatively warmtemperature. The coating obstructs the permeation of the fabric by suchgas, thereby permitting the cushion to rapidly inflate without unduedecompression during a collision event.

Airbags may also be formed from uncoated fabric which has been woven ina manner that creates a product possessing low permeability or fromfabric that has undergone treatment such as calendaring to reducepermeability. Fabrics which reduce air permeability by calendaring orother mechanical treatments after weaving are disclosed in U.S. Pat. No.4,921,735; U.S. Pat. No. 4,977,016; and U.S. Pat. No. 5,073,418 (allincorporated herein by reference).

Silicone coatings typically utilize either solvent based or complex twocomponent reaction systems. Dry coating weights for silicone have beenin the range of about 3 to 4 ounces per square yard or greater for boththe front and back panels of side curtain airbags. As will beappreciated by one of ordinary skill in this art, high add on weightssubstantially increase the cost of the base fabric for the airbag andmake packing within small airbag modules very difficult. Furthermore,silicone exhibits very low tensile strength characteristics that do notwithstand high pressure inflation easily without the utilization of verythick coatings.

The use of a particular type of polyurethane as a coating as disclosedin U.S. Pat. No. 5,110,666 to Menzel et al. (herein incorporated byreference) permits low add on weights reported to be in the range of 0.1to 1 ounces per square yard but the material itself is relativelyexpensive and is believed to require relatively complex compounding andapplication procedures due to the nature of the coating materials.Patentees, however, fails to disclose any pertinent elasticity and/ortensile strength characteristics of their particular polyurethanecoating materials. Furthermore, there is no discussion pertaining to theimportance of the coating ability (and thus correlated low airpermeability) at low add-on weights of such polyurethane materials onside curtain airbags either only for fabrics which are utilized withindriver or passenger side cushions. All airbags must be inflatableextremely quickly; upon sensing a collision, in fact, airbags usuallyreach peak pressures within 10 to 20 milliseconds. Regular driver sideand passenger side air bags are designed to withstand this enormousinflation pressure; however, they also deflate very quickly in order toeffectively absorb the energy from the vehicle occupant hitting the bag.Such driver and passenger side cushions (airbags) are thus made from lowpermeability fabric, but they also deflate quickly at connecting seams(which are not coated to prevent air leakage) or through vent holes.Furthermore, the low add-on coatings taught within Menzel, and withinU.S. Pat. No. 5,945,186 to Li et al., would not provide long-tern gasretention; they would actually not withstand the prolonged andcontinuous pressures supplied by activated inflators for more than about2 seconds, at the most. The low permeability of these airbag fabricsthus aid in providing a small degree of sustained gas retention withindriver and passenger airbag cushions to provide the deflating cushioningeffects necessary for sufficient collision protection. Such airbagfabrics would not function well with side curtain airbags, since, at thevery least, the connecting seams which create the pillowed, cushionedstructures within such airbags, as discussed in greater detail below,would exhibit too high a leakage rate upon inflation at requisite highgas pressures. As these areas provide the greatest degree of leakageduring and after inflation, the aforementioned patented low coating lowpermeability airbag fabrics would not be properly utilized within sidecurtain airbags, in particular side curtain airbags intended to provideextended rollover protection.

As alluded to above, there are three primary types of different airbags,each for different end uses. For example, driver-side airbags aregenerally mounted within steering columns and exhibit relatively highair permeabilities in order to act more as a cushion for the driver uponimpact. Passenger-side airbags also comprise relatively high airpermeability fabrics which permit release of gas either therethrough orthrough vents integrated therein. Both of these types of airbags aredesigned to protect persons in sudden collisions and generally burst outof packing modules from either a steering column or dashboard (and thushave multiple “sides”). Side curtain airbags, however, have beendesigned primarily to protect passengers during side crashes providerollover protection by retaining their inflation state for a longduration, and generally unroll from packing containers stored within theroofline along the side windows of an automobile (and thus have a backand front side only). Side curtain airbags therefore not only providecushioning effects but also provide protection from broken glass andother debris. As such, it is imperative that side curtain airbags, asnoted above, retain large amounts of gas, as well as high gas pressures,to remain inflated throughout the longer time periods of the entirepotential rollover situation. To accomplish this, these side curtainsare generally coated with very large amounts of sealing materials onboth the front and back sides. Since most side curtain airbag fabricscomprise woven blanks that are either sewn, sealed, or integrally woventogether, discrete areas of potentially high leakage of gas areprevalent, particularly at and around the seams. It has been accepted asa requirement that heavy coatings were necessary to provide the lowpermeability (and thus high leak-down time) necessary for side curtainairbags. Without such heavy coatings, such airbags would most likelydeflate too quickly and thus would not function properly during arollover collision. As will be well understood by one of ordinary skillin this art, such heavy coatings add great cost to the overallmanufacture of the target side curtain airbags. There is thus a greatneed to manufacture low permeability side curtain airbags with lessexpensive (preferably lower coating add-on weight) coatings withoutlosing the aging, stability, and permeability characteristics necessaryfor proper functioning upon deployment. To date, there has been littleaccomplished, if anything at all, alleviating the need for such thickand heavy airbag coatings from side curtain airbags.

Furthermore, there is a current drive to store such low permeabilityside curtain airbags within cylindrically shaped modules. Since theseairbags are generally stored within the rooflines of automobiles, andthe area available is quite limited, there is always a great need torestrict the packing volume of such restraint cushions to their absoluteminimum. However, the previously practiced low permeability side curtainairbags have proven to be very cumbersome to store in such cylindricallyshaped containers at the target automobile's roofline. The actual timeand energy required to roll such heavily coated low permeabilityarticles as well as the packing volume itself, has been very difficultto reduce. Furthermore, with such heavy coatings utilized, the problemsof blocking (i.e., adhering together of the different coated portions ofthe cushion) are amplified when such articles are so closely packedtogether. The chances of delayed unrolling during inflation are raisedwhen the potential for blocking is present. Thus, a very closely packed,low packing volume, low blocking side curtain low permeability airbag ishighly desirable. Unfortunately, the prior art has again not accordedsuch an advancement to the airbag industry.

OBJECTS AND BRIEF DESCRIPTION OF THE INVENTION

In light of the background above, it can be readily seen that thereexists a need for a low permeability, side curtain airbag that utilizeslower, and thus less expensive, amounts of coating, and thereforeexhibits a substantially reduced packing volume over the standard lowpermeability type side curtain airbags. Such a coated low permeabilityairbag must provide a necessarily long leak-down time upon inflation andafter long-term storage. Such a novel airbag and a novel coatingformulation provides marked improvements over the more expensive, muchhigher add-on airbag coatings (and resultant airbag articles) utilizedin the past.

It is therefore an object of this invention to provide a coated airbag,wherein the coating is present in a very low add-on weight, possessingextremely high leak-down time characteristics after inflation and thuscomplementary low permeability characteristics. Another object of theinvention is to provide an inexpensive side curtain airbag cushion. Afurther object of this invention is to provide an highly effectiveairbag coating formulation which may be applied in very low add-onamounts to obtain extremely low permeability airbag structures afterinflation. An additional object of this invention is to provide anairbag coating formulation which not only provides beneficial andlong-term low permeability, but also exhibits excellent long-termstorage stability (through heat aging and humidity aging testing). Yetanother object of the invention is to provide a low permeability sidecurtain airbag possessing a very low rolled packing volume andnon-blocking characteristics for effective long-term storage within theroofline of an automobile.

Accordingly, this invention is directed to an airbag cushion comprisinga coated fabric, wherein said fabric is coated with an elastomericcomposition in an amount of at most 3.0 ounces per square yard of thefabric; and wherein said airbag cushion, after long-term storage,exhibits a characteristic leak-down time of at least 5 seconds. Also,this invention concerns an airbag cushion comprising a coated fabric,wherein said fabric is coated with an elastomeric composition; whereinsaid elastomeric composition comprises at least one elastomer possessinga tensile strength of at least 2,000 psi and an elongation of at last180%; and wherein said airbag cushion, after long-term storage, exhibitsa characteristics leak-down time of at least 5 seconds. Additionally,this invention encompasses a coated airbag cushion which exhibits arolled packing volume factor (measured as the rolled diameter of theairbag cushion to depth of coverage measured from the attachment pointof the target automobile's roofline to lowest point of coverage belowthe roofline after inflation) of at least 17.

The term “characteristic leak-down time” is intended to encompass themeasurement of time required for the entire amount of inflation gasintroduced within an already-inflated (to a peak initial pressure which“opens” up the areas of weak sealing) and deflated airbag cushion uponsubsequent re-inflation at a constant pressure at 10 psi. It is wellknown and well understood within the airbag art, and particularlyconcerning side curtain (low permeability) airbag cushions, thatretention of inflation gas for long periods of time is of utmostimportance during a collision that results in rollover and othersubsequent problems. Side curtain airbags are designed to inflate asquickly as driver- and passenger-side bags, but they must deflate veryslowly to protect the occupants during roll over and side impact. Thus,it is imperative that the bag exhibit a very low leakage rate after thebag experiences peak pressure during the instantaneous, quick inflation.Hence, the coating on the bag must be strong enough to withstand theshock and stresses when the bag is inflated so quickly. Thus, a highcharacteristic leak-down time measurement is paramount in order toretain the maximum amount of beneficial cushioning gas within theinflated airbag. Airbag leakage after inflation (and after peak pressureis reached) is therefore closely related to actual pressure retentioncharacteristics. The pressure retention characteristics (hereinafterreferred to as “leak-down time”) of already-inflated and deflated sidecurtain airbags can be described by a characteristic leak-down time t,wherein:${t({second})} = {\frac{{Bag}\quad {volume}\quad \left( {ft}^{3} \right)}{{Volumetric}\quad {leakage}\quad {{rate}\left( {SCFH}^{*} \right)}\quad {at}\quad 10\quad {Psi}} \times 3600}$

*SCFH: standard cubic feet per hour.

It is understood that the 10 psi constant is not a limitation to theinvention; but merely the constant pressure at which the leak-down timemeasurements are made. Thus, even if the pressure is above or below thisamount during actual inflation or after initial pressurizing of theairbag, the only limitation is that if one of ordinary skill in the artwere to mere the bag volume and divide that by the volumetric leakagerate (at 10 psi), the resultant measurement in time would be at least 5seconds. Preferably, this time is greater than about 9 seconds; morepreferably, greater than about 15 seconds; and most preferably, greaterthan about 20 seconds.

Alternatively, and in a manner of measurement with uninflated sidecurtain airbags, the term “leak-down time” may be measured as the amountof time required for at half of the introduced inflation gas to escapefrom the target airbag after initial peak pressure is reached. Thus,this measurement begins the instant after peak initial pressure isreached upon inflation (such as, traditionally, about 30 psi) with astandard inflation module which continues to pump gas into the targetairbag during and after peak initial pressure is reached. It is wellunderstood that the pressure of gas forced into the airbag after peakinitial pressure is reached will not remain stable (it decreases duringthe subsequent introduction of inflation gas), and that the targetairbag will inevitably permit escape of a certain amount of inflationgas during that time. The primary focus of such side curtain airbags (asnoted above) is to remain inflated for as long as possible in order toprovide sufficient cushioning protection to vehicle occupants duringrollover accidents. The greater amount of gas retained, the bettercushioning effects are provided the passengers. Thus, the longer theairbag retains a large amount of inflation gas, and consequently thegreater the characteristic leak-down time, the better cushioning resultsare achieved. At the very least, the inventive airbag must retain atleast half of its inflated gas volume 5 seconds subsequent to reachingpeak initial pressure. Preferably, this time is 9 seconds, morepreferably 15 seconds, and most preferably 20 seconds.

Likewise, the term, “after long-term storage” encompasses either theactual storage of an inventive airbag cushion within an inflatorassembly (module) within an automobile and/or in a storage facilityawaiting installation. Furthermore, this term also encompasses anystorage which is intended to simulate such long-term storage (throughoven-aging, as one example) as well. Such a measurement is generallyaccepted, and is well understood and appreciated by the ordinarilyskilled artisan, to be made through comparable analysis afterrepresentative heat and humidity aging tests. These tests generallyinvolve 107° C. oven aging for 400 hours, followed by 83° C. and 95%relative humidity aging for a subsequent 400 hours and are universallyaccepted as proper estimations of the conditions of long-term storagefor airbag cushions. Thus, this term encompasses such measurement tests.The inventive airbag fabrics must exhibit proper characteristicleak-down times after undergoing such rigorous pseudo-storage testing.

The inventive elastomeric coating composition must comprise at least oneelastomer that possesses a tensile strength of at least 2,000 psi and anelongation to break of greater than about 180%. Preferably, the tensilestrength is at least 3,000 psi more preferably, 4,000, and mostpreferably at least about 6,000 (the high end is basically the highestone can produce which can still adhere to a fabric surface). Thepreferred elongation to break is more than about 200%, more preferablymore than about 300%, and most preferably more than about 600%. Thesecharacteristics of the elastomer translate to a coating that is bothvery strong (and thus will withstand enormous pressures both atinflation and during the time after inflation and will not easily break)and can stretch to compensate for such large inflation, etc., pressures.Thus, when applied at the seams of a side curtain airbag, as well asover the rest of the airbag structure, the coating will most preferably(though not necessarily) form a continuous film. This coating acts toboth fill the individual holes between the woven yarns and/or stitches,etc, as well as to “cement” the individual yarns in place. Duringinflation, then, the coating prevents leakage through the interstitialspaces between the yarns and aids in preventing yarn shifting (which maycreate larger spaces for possible gas escape).

The utilization of such high tensile strength and high elongation atbreak components permits the consequent utilization, surprisingly, ofextremely low add-on weight amounts of such coating formulations.Normally, the required coatings on side curtain airbags are very high,at least 3.0 ounces per square yard (with the standard actually muchhigher than that, at about 4.0). The inventive airbag cushions requireat most 3.0 (preferably less, such as 2.0, more preferably 1.8, stillmore preferably, about 1.5, and most preferably, as low as 0.8) ouncesper square yard of this inventive coating to effectuate the desired highleak-down (low permeability). Furthermore, the past coatings wererequired to exhibit excellent heat and humidity aging stability.Unexpectedly, even at such low add-on amounts, and particularly withhistorically questionable coating materials (polyurethanes, forexample), the inventive coatings, and consequently, the inventive coatedairbag cushions, exhibit excellent heat aging and humidity agingcharacteristics. Thus, the coating compositions and coated airbags areclearly improvements within this specific airbag art.

Of particular interest as the elastomer components within the inventiveelastomeric compositions are, specifically, polyamides, polyurethanes,acrylic elastomers, hydrogenated nitrile rubbers (i.e., hydrogenatedNBR), fluoroelastomers (i.e., fluoropolymers and copolymers containingfluoro-monomers), ethylene-vinylacetate copolymers, and ethyleneacrylate copolymers. Also, such elastomers may or may not becross-linked on the airbag surface. Preferably, the elastomer is apolyurethane and most preferably is a polycarbonate polyurethaneelastomer. Such a compound is available from Bayer Corporation under thetradename IMPRANIL®, including IMPRANIL® 85 UD, ELH, and EHC-01. Otheracceptable polyurethanes include BAYHYDROL® 123, also from Bayer; Ru41-710, EX 51-550, and Ru 40-350, both from Stahl USA. Any polyurethane,or elastomer, for that matter, which exhibits the same tensile strengthand elongation at break characteristics as noted above, however, arepotentially available within the inventive coating formulation and thuson the inventive coated airbag cushion. In order to provide the desiredleak-down times at long-term storage, however, the add-on weights ofother available elastomers may be greater than others. However, theupper limit of 3.0 ounces per square yard should not be exceeded to meetthis invention. The desired elastomers may be added in multiple layersif desired as long the required thickness for the overall coating is notexceeded. Alternatively, the multiple layer coating system may also beutilized as long as at least one elastomer possessing the desiredtensile strength and elongation at break is utilized.

Other possible components present within the elastomer coatingcomposition are thickeners, antioxidants, flame retardants, coalescentagents, adhesion promoters, and colorants. In accordance with thepotentially preferred practices of the present invention, a dispersion(either solvent- or water-borne, depending on the selected elastomer) offinely divided elastomeric resin is compounded, or present in a resinsolution, with a thickener and a flame retardant to yield a compoundedmix having a viscosity of about 8000 centipoise or greater. Apolyurethane is potentially preferred, with a polycarbonatepolyurethane, such as those noted above from Bayer and Stahl, mostpreferred. Other potential elastomeric resins include otherpolyurethanes, such as WICOBOND™ 253 (35% solids), from Witco, andSANCURE®, from BFGoodrich; Cleveland, Ohio; hydrogenated NBR, such asCHEMISAT™ LCH-7335X (40% solids), from Goodyear Chemical, Akron, Ohio;EPDM, such as EP-603A rubber latex, from Lord Corporation, Erie, Pa.;butyl rubber, such as Butyl rubber latex BL-100, from Lord Corporation;and acrylic rubber (elastomers), such as HYCAR™, from BFGoodrich. Thislist should not be understood as being all-inclusive, only exemplary ofpotential elastomers. Furthermore, the preferred elastomer will notinclude any silicone, due to the extremely low tensile strength(typically below about 1,500 psi) characteristics exhibited by suchmaterials. However, in order to provide effective aging and non-blockingbenefits, such components may be applied to the elastomeric compositionas a topcoat as long as the add-on weight of the entire elastomer andtopcoat does not exceed 3.0 ounces per square yard and the amount ofsilicone within the entire elastomer composition does not exceed 20% byweight. Additionally, certain elastomers comprising polyester orpolyether segments or other similar components, may not be undesirable,particularly at very low add-on weights (i.e., 0.8-1.2 oz/yd²) due tostability problems in heat and humidity aging (polyesters easilyhydrolyze in humidity and polyethers easily oxidize in heat); however,such elastomers may be utilized in higher add-on amounts as long, again,as the 3.0 ounces per square yard is not exceeded.

Among the other additives particularly preferred within this elastomercomposition are heat stabilizers, flame retardants, primer adhesives,and materials for protective topcoats. A potentially preferred thickeneris marketed under the trade designation NATROSOL™ 250 HHXR by theAqualon division of Hercules Corporation which is believed to have aplace of business at Wilmington, Del. In order to meet Federal MotorVehicle Safety Standard 302 flame retardant requirements for theautomotive industry, a flame retardant is also preferably added to thecompounded mix. One potentially preferred flame retardant is AMSPERSE®F/R 51 marketed by Amspec Chemical Corporation which is believed to havea place of business at Gloucester City N.J. Primer adhesives may beutilized to facilitate adhesion between the surface of the target fabricand the elastomer itself. Thus, although it is preferable for theelastomer to be the sole component of the entire elastomer compositionin contact with the fabric surface, it is possible to utilize adhesionpromoters, such as isocyanates, epoxies, functional silanes, and othersuch resins with adhesive properties, without deleteriously effectingthe ability of the elastomer to provide the desired low permeability forthe target airbag cushion. A topcoat component, as with potentialsilicones, as noted above, may also be utilized to effectuate propernon-blocking characteristics to the target airbag cushion. Such atopcoat may perform various functions, including, but not limited to,improving aging of the elastomer (such as with silicone) or providingblocking resistance due to the adhesive nature of the coating materials(most noticeably with the preferred polyurethane polycarbonates).

Airbag fabrics must pass certain tests in order to be utilized withinrestraint systems. One such test is called a blocking test whichindicates the force required to separate two portions of coated fabricfrom one another after prolonged storage in contact with each other(such as an airbag is stored). Laboratory analysis for blocking entailspressing together coated sides of two 2 inch by 2 inch swatches ofairbag fabric at 5 psi at 100° C. for 7 days. If the force required topull the two swatches apart after this time is greater than 50 grams, orthe time required to separate the fabrics utilizing a 50 gram weightsuspended from the bottom fabric layer is greater than 10 seconds, thecoating fails the blocking test. Clearly, the lower the requiredseparating shear force, the more favorable the coating. For improvedblocking resistance (and thus the reduced chance of improper adhesionbetween the packed fabric portions), topcoat components may be utilized,such as talc, silica, silicate clays, and starch powders, as long as theadd-on weight of the entire elastomer composition (including thetopcoat) does not exceed 3.0 ounces per square yard (and preferablyexists at a much lower level, about 1.5, for instance).

Two other tests which the specific coated airbag cushion must pass arethe oven (heat) aging and humidity aging tests. Such tests also simulatethe storage of an airbag fabric over a long period of time upon exposureat high temperatures and at relatively high humidities. These tests areactually used to analyze alterations of various different fabricproperties after such a prolonged storage in a hot ventilated oven(>100° C.) (with or without humid conditions) for 2 or more weeks. Forthe purposes of this invention, this test was used basically to analyzethe air permeability of the coated side curtain airbag by measuring thecharacteristic leak-down time (as discussed above, in detail). Theinitially produced and stored inventive airbag cushion should exhibit acharacteristic leak-down time of greater than about 5 seconds (uponre-inflation at 10 psi gas pressure after the bag had previously beeninflated to a peak pressure above about 15 psi and allowed to fullydeflate) under such harsh storage conditions. Since polyurethanes, thepreferred elastomers in this invention, may be deleteriously affected byhigh heat and humidity (though not as deleteriously as certain polyesterand polyether-containing elastomers), it may be prudent to add certaincomponents within a topcoat layer and/or within the elastomer itselfAntioxidants, antidegradants, and metal deactivators may be utilized forthis purpose. Examples include, and are not intended to be limited to,IRGANOX® 1010 and IRGANOX® 565, both available from CIBA SpecialtyChemicals. This topcoat may also provide additional protection againstaging and thus may include topcoat aging improvement materials, such as,and not limited to, polyamides, NBR rubbers, EPDM rubbers, and the like,as long as the elastomer composition (including the topcoat) does notexceed the 3.0 ounces per square yard (preferably much less than that,about 1.5 at the most) of the add-on weight to the target fabric.

Other additives may be present within the elastomer composition,including, and not limited to, colorants, UV stabilizers, fillers,pigments, and crosslinking/curing agents, as are well known within thisart.

The substrate to which the inventive elastomeric coatings are applied toform the airbag base fabric in accordance with the present invention ispreferably a woven fabric formed from yarns comprising synthetic fibers,such as polyamides or polyesters. Such yarn preferably has a lineardensity of about 105 denier to about 840 denier, more preferably fromabout 210 to about 630 denier. Such yarns are preferably formed frommultiple filaments wherein the filaments have linear densities of about6 denier per filaments or less and most preferably about 4 denier perfilament or less. In the more preferred embodiment such substrate fabricwill be formed from fibers of nylon, and most preferred is nylon 6,6. Ithas been found that such polyamide materials exhibit particularly goodadhesion and maintenance of resistance to hydrolysis when used incombination with the coating according to the present invention. Suchsubstrate fabrics are preferably woven using fluid jet weaving machinesas disclosed in U.S. Pat. Nos. 5,503,197 and 5,421,378 to Bower et al.(incorporated herein by reference). Such woven fabric will behereinafter referred to as an airbag base fabric. As noted above, theinventive airbag must exhibit extremely low permeability and thus mustbe what is termed a “side curtain” airbag. As noted previously andextensively, such side curtain airbags (a.k.a., cushions) must retain alarge amount of inflation gas during a collision in order to accordproper long-duration cushioning protection to passengers during rolloveraccidents. Any standard side curtain airbag may be utilized incombination with the low add-on coating to provide a product whichexhibits the desired leak-down times as noted above. Most side curtainairbags arm produced through labor-intensive sewing or stitching (orother manner) together two separate woven fabric blanks to form aninflatable structure. Furthermore, as is well understood by theordinarily skilled artisan, such sewing, etc., is performed in strategiclocations to form seams (connection points between fabric layers) whichin turn produce discrete open areas into which inflation gasses may flowduring inflation. Such open areas thus produce pillowed structureswithin the final inflated airbag cushion to provide more surface areaduring a collision, as well as provide strength to the bag itself inorder to withstand the very high initial inflation pressures (and thusnot explode during such an inflation event). Other side curtain airbagcushions exist which are of the one-piece woven variety. Basically, someinflatable airbags are produced through the simultaneous weaving of twoseparate layers of fabric which are joined together at certain strategiclocations (again, to form the desired pillowed structures). Suchcushions thus present seams of connection between the two layers. It isthe presence of so many seams (in both multiple-piece and one-piecewoven bags) which create the aforementioned problems of gas loss duringand after inflation. The possibility of yarn shifting, particularlywhere the yarns shift in and at many different ways and amounts, thuscreates the quick deflation of the bag through quick escaping ofinflation gasses. Thus, the base airbag fabrics do not provide much helpin reducing permeability (and correlated leak-own times, particularly atrelatively high pressures). It is this seam problem which has primarilycreated the need for the utilization of very thick, and thus expensive,coatings to provide necessarily low permeability in the past.

Recently, a move has been made away from both the multiple-piece sidecurtain airbags (which require great amounts of labor-intensive sewingto attached woven fabric blanks) and the traditionally producedone-piece woven cushions, to more specific one-piece woven fabrics whichexhibit substantially reduced floats between woven yarns tosubstantially reduce the unbalanced shifting of yarns upon inflation,such as in Ser. No. 09/406,264, now U.S. Pat. No. 6,220,309, and Ser.No. 09/668,857, both to Sollars, Jr., the specifications of which arecompletely incorporated herein and described in greater depth hereafter:

The term “inflatable fabric” hereinafter is intended to encompass anyfabric which is constructed of at least two layers of fabric which canbe sealed to form a bag article. The inventive inflatable fabric thusmust include double layers of fabric to permit such inflation, as wellas single layers of fabric either to act as a seal at the ends of suchfabric panels, or to provide “pillowed” chambers within the targetfabric upon inflation. The term “all-woven” as it pertains to theinventive fabric thus requires that the inflatable fabric having doubleand single layers of fabric be produced solely upon a loom. Any type ofloom may be utilized for this purpose, such as water-jet, air-jet,rapier, and the like. Patterning may be performed utilizing Jacquardweaving and/or dobby weaving, particularly on fluid-jet and/or highspeed rapier loom types.

The constructed fabric may exhibit balanced or unbalanced pick/endcounts; the main requirement in the woven construction is that thesingle layer areas of the inflatable fabric exhibit solely basket-weavepatterns. These patterns are made through the arrangement of at leastone warp yarn (or weft yarn) configured around the same side of twoadjacent weft yarns (or warp yarns) within the weave pattern. Theresultant pattern appears as a “basket” upon the arrangement of the samewarp (or weft) yarn to the opposite side of the next adjacent weft (orwarp) yarn. Such basket weave patterns may include the arrangement of awarp (or weft) yarn around the same side of any even number of weft (orwarp) yarns, preferably up to about six at any one time, most preferablyup to about 4.

The sole utilization of such basket weave patterns in the single layerzones provides a number of heretofore unexplored benefits withininflatable fabric structures. For example, such basket weave patternspermit a constant “seam” width and weave construction over an entiresingle layer area, even where the area is curved. As noted above, thestandard Oxford weaves currently utilized cannot remain as the sameweave pattern around curved seams; they become plain weave patterns.Also, such basket weave seam patterns permit the construction of aninflatable fabric having only plain woven double layer fabric areas andsingle layer “seams” with no “floats” of greater than three picks withinthe entire fabric structure. Such a fabric would thus not possessdiscrete locations where the air permeability is substantially greaterthan the remaining portions of the fabric. Additionally, such a weavestructure permits the utilization of as low as two different weavedensities (patterns, etc.) in the area of the produced seam. Thus, theseam itself is of one weave pattern and the weave pattern in the areadirectly adjacent to the seam is another weave pattern. No otherpatterns are utilized in that specific seam area. By directly adjacent,it is intended that such a described area is within at most 14yarn-widths, preferably as low as 2 yarn-widths, and most preferablybetween about 4 and 8 yarn-widths, from the actual seam itself. Such alimitation on different weave densities has never been accomplished inall-woven airbags in the past.

Generally, the prior art (such as Thornton et al., supra) provides seamattachments exhibited at least three different weave densities withinthe directly adjacent area of the seams themselves. Furthermore, theprior art weaving procedures produce floats of sometimes as much as sixor seven picks at a time. Although available software to the weavingindustry permits “filling in” of such floats within weave diagrams, sucha procedure takes time and still does not continuously provide a fabricexhibiting substantially balanced air permeability characteristics overthe entire structure. The basket-weave formations within the singlefabric layers thus must be positioned in the fabric so as to preventirregularities (large numbers of floats, for example) in the weaveconstruction at the interface between the single and double fabriclayers (as described in FIG. 2, below). Another benefit such basketweave patterns accord the user is the ability to produce more than onearea of single layer fabric (i.e., another “seam” within the fabric)adjacent to the first “seam.” Such a second seam provides a manner ofdissipating the pressure from or transferring the load upon eachindividual yarn within both seams. Such a benefit thus reduces thechances of deleterious yarn shifting during an inflation event throughthe utilization of strictly a woven fabric construction (i.e., notnecessarily relying upon the utilization of a coating as well). Thepreviously disclosed or utilized inflatable fabrics having both doubleand single fabric layer areas have not explored such a possibility inutilizing two basket-weave pattern seams. Furthermore, such a two-seamconstruction eliminates the need for weaving a large single fabric layerarea within the target inflatable fabric. The prior art fabrics whichproduce “pillowed” chambers for airbag cushions (such as side curtains),have been formed through the weaving of entire areas of single fabriclayers (which are not actually seams themselves). Such a procedure istime-consuming and rather difficult to perform. The inventive inflatablefabric merely requires, within this alternative embodiment, at least twovery narrow single fabric layer areas (seams) woven into the fabricstructure (another preferred embodiment utilizes merely one seam ofsingle layer fabric); the remainder of the fabric located within thesetwo areas may be double layer if desired. Thus, the inventive fabricpermits an improved, cost-effective, method of making a “pillowed”inflatable fabric.

The inflatable fabric itself is preferably produced from all-syntheticfibers, such as polyesters and polyamides, although natural fibers mayalso be utilized in certain circumstances. Preferably, the fabric isconstructed of nylon-6,6. The individual yarns utilized within thefabric substrate must generally possess deniers within the range of fromabout 40 to about 840; preferably from about 100 to about 630.

As noted above, coatings should be applied to the surface as a necessarysupplement to reduce the air permeability of the inventive fabric. Sinceone preferred ultimate use of this inventive fabric is as a side curtainairbag which must maintain a very low degree of air permeabilitythroughout a collision event (such as a rollover where the curtain mustprotect passengers for an appreciable amount of time), a decrease inpermitted air permeability is highly desirable. With such a specificweaving pattern within the inventive inflatable fabric, lower amounts ofcoatings are permissible (as compared to other standard additions ofsuch materials) to provide desired low inflation gas permeability. Anystandard coating or laminate film, such as a silicone, polyurethane,polyamide, polyester, rubber (such as neoprene, for example), and thelike, as discussed above, may be utilized for this purpose and may beapplied in any standard method and in any standard amount on the fabricsurface. However, the necessary amount of such a coating (or layers ofcoatings or laminate film or layer of laminate films) required toprovide the desired low permeability is extremely low and is discussedin greater depth above. Again, the particular weave structures of theinventive inflatable fabric permits the utilization of such low coatingamounts to provide the desired low permeability characteristics.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice for the invention. It isto be understood that both the foregoing general description and thefollowing detailed description of preferred embodiments are exemplaryand explanatory only, and are not to be viewed as in any way restrictingthe scope of the invention as set forth in the claims.

With such an improvement in one-piece side curtain airbags (andinflatable fabrics), the possibility of high leakage at seams issubstantially reduced. These airbags provide balanced weaveconstructions at and around attachment points between two layers offabrics such that the ability of the yarns to become displaced uponinflation at high pressures is reduced as compared with the standardone-piece woven airbags. Unfortunately, such inventive one-piece wovenbags are still problematic in that the weave intersections may bedisplaced upon high pressure inflation such that leakage will still mostlikely occur at too high a rate for proper functioning. As a result,there is still a need to coat such one-piece woven structures withmaterials which reduce and/or eliminate such an effect. However, suchone-piece woven structures permit extremely low add-on amounts ofelastomeric coatings for low permeability effects. In fact, theseinventive airbags function extremely well with low add-on coatings below1.5 and as low as about 0.8 ounces per square yard.

Furthermore, although it is not preferred in this invention, it has beenfound that the inventive coating composition provides similar lowpermeability benefits to standard one-piece woven airbags, particularlywith the inventive low add-on amounts of high tensile strength, highelongation, non-silicone coatings; however, the amount of coatingrequired to permit high leak-down times is much higher than for theaforementioned Sollars, Jr. inventive one-piece woven structure. Thus,add-on amounts of as much as 1.5 and even up to about 2.2 ounces persquare yard may be necessary to effectuate the proper low level of airpermeability for these other one piece woven airbags. Even with suchhigher add-on coatings, the inventive coatings themselves clearlyprovide a marked improvement over the standard, commercial, prior artsilicone, etc., coatings (which must be present in amounts of at least3.0 ounces per square yard).

Additionally, it has also been found that the inventive coatingcompositions, at the inventive add-on amounts, etc., provide the sametypes of benefits with the aforementioned sewn, stitched, etc., sidecurtain airbags. Although such structures are highly undesirable due tothe high potential for leakage at these attachment seams, it has beenfound that the inventive coating provides a substantial reduction inpermeability (to acceptable leak-down time levels, in fact) withcorrelative lower add-on amounts than with standard silicone andneoprene rubber coating formulations. Such add-on amounts will approachthe 3.0 ounces per square yard, but lower amounts have proven effective(1.5 ounces per square yard, for example) depending on the utilizationof a sufficiently high tensile strength and sufficiently stretchableelastomeric component within the coating composition directly in contactwith the target fabric surface. Again, with the ability to reduce theamount of coating materials (which are generally always quiteexpensive), while simultaneously providing a substantial reduction inpermeability to the target airbag structure, as well as high resistanceto humidity and extremely effective aging stability, the inventivecoating composition, and the inventive coated airbag itself is clearly avast improvement over the prior airbag coating art.

Of particular importance within this invention, is the ability to packthe coated airbag cushions within cylindrical storage containers at theroof line of a target automobile in as small a volume as possible. In arolled configuration (in order to best fit within the cylindricalcontainer itself, and thus in order to best inflate upon a collisionevent downward to accord the passengers sufficient protection), theinventive airbag may be constricted to a cylindrical shape having adiameter of at most 23 millimeters. In such an instance, with a 2 meterlong cylindrical roofline storage container, the necessary volume ofsuch a container would equal about 830 cm³.(with the volume calculatedas 2[Pi]radius²) Standard rolled packing diameters are at least 25millimeters for commercially available side curtain airbag cushions (dueto the thickness of the required coating to provide low permeabilitycharacteristics). Thus, the required cylindrical container volume wouldbe at least 980 cm³. Preferably, the rolled diameter of the inventiveairbag cushion during storage is at most 20 millimeters (giving a packedvolume of about 628 cm³) which is clearly well below the standardpacking volume. In relation, then, to the depth of the airbag cushionupon inflation (i.e., the length the airbag extends from the rooflinedown to its lowest point along the side of the target automobile, suchas at the windows), the quotient of the inventive airbag cushion's depth(which is standard at approximately 17 inches or 431.8 millimeters) toits rolled packed diameter should be at least about 18.8. Preferablythis quotient should be about 21.6 (20 millimeter diameter), and, at itsmaximum, should be about 24 (with a minimum diameter of about 18millimeters). Of course, this range of quotients does not require thedepth to be at a standard of 17 inches, and is primarily a function ofcoating thickness, and thus add-on weight.

Surprisingly, it has been discovered that any elastomer with a tensilestrength of at least 2,000 psi and an elongation at break of at least180% coated onto and over both sides of a side curtain airbag fabricsurface at a weight of at most 3.0 ounces per square yard, andpreferably between 0.8 and 2.0, more preferably from 0.8 to about 1.5,still more preferably from 0.8 to about 1.2, and most preferably about0.8 ounces per square yard, provides a coated airbag cushion whichpasses both the long-term blocking test and long-term oven aging testwith very low, and extended permeability upon and after inflation. Thisunexpectedly beneficial type and amount of coating thus provides anairbag cushion which will easily inflate after prolonged storage andwill remain inflated for a sufficient amount of time to ensure anoptimum level of safety within a restraint system. Furthermore, it goeswithout saying that the less coating composition required, the lessexpensive the final product. Additionally, the less coating compositionrequired will translate into a decrease in the packaging volume of theairbag fabric within an airbag device. This benefit thus improves thepackability for the airbag fabric.

While the invention will be described and disclosed in connection withcertain preferred embodiments and practices, it is in no way intended tolimit the invention to those specific embodiments, rather it is intendedto cover equivalent structures structural equivalents and allalternative embodiments and modifications as may be defined by the scopeof the appended claims and equivalence thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Two potentially preferred elastomer compositions of this invention waspreferably produced in accordance with the following Tables:

TABLE 1 Standard Water-Borne Elastomer Composition Component Parts (perentire composition) Resin (30-40% solids content in water) 100Natrosol ® 250 HHXR (thickener) 10 Irganox ® 1010 (stabilizer) 0.5 DE-83R (flame retardant) 10

TABLE 2 Standard Solvent-Borne Elastomer Composition Component Parts(per entire composition) Resin (30-40% solids content in solvent) 100Irganox ® 1010 (stabilizer) 0.5 DE-83 R (flame retardant) 10

TABLE 3 Standard Solvent-Borne Elastomer Composition Component Parts(per entire composition) Resin (25-40% solids content in solvent) 100Irganox ® 1010 (stabilizer) 0.5 DE-83 R (flame retardant) 10 DesmodurCB-75 (adhesion promoter) 2

(The particular resins are listed below in Table 4 and thus are merelyadded within this standard composition in the amount listed to formpreferred embodiments of the inventive coating formulation).

The compounded compositions exhibited viscosities measured to be about15,000 centipoise by a Brookfield viscometer. Once compounding wascomplete, the individual formulations were applied to separate articlesbeing both sides of one-piece Jacquard woven airbags (having 420 deniernylon 6,6 yarns therein) as discussed within the Sollars, Jr.application noted above. Such applications were performed through afixed gap coating procedure. The bag were then dried at an elevatedtemperature (about 300° F. for about 3 minutes) and thus form to formthe necessarily thin coatings. As noted above, scrape coating may alsobe followed to provide the desired film coating; however, fixed gapcoating provides the desired film thickness uniformity on the bagsurface and thus is preferred. Scrape coating, in this sense, includes,and is not limited to, knife coating, in particular knife-over-gaptable, floating knife, and knife-over-foam pad methods. The final dryweight of the coating is preferably from about 0.6-3.0 ounces per squareyard or less and most preferably 0.8-1.5 ounces per square yard or less.The resultant airbag cushion is substantially impermeable to air whenmeasured according to ASTM Test D737, “Air Permeability of TextileFabrics,” standards.

In order to further describe the present invention the followingnon-limiting examples are set forth. These examples are provided for thesole purpose of illustrating some preferred embodiments of the inventionand are not to be construed as limiting the scope of the invention inany manner. These examples involve the incorporation of the below-notedpreferred elastomers within the coating formulations of TABLES 1-3,above.

Each coated bag was first subjected to quick inflation to a peakpressure of 30 Psi. Air leakage (SCFH) of the inflated bag was thenmeasured at 10 Psi pressure. The characteristic leak-down time t(sec)was calculated based on the leakage rate and bag volume.

TABLE 4 Coating Tensile Elonga- T (sec). T (sec.) add- Example Number/Strength tion at Before Post- on weight Elastomer (Psi) break (%) agingaging* (oz/yd2) 1. Impranil ® 85 6000 400 18.1 16.3 0.8 UD 2. Ex 51-5503100 320 110.2 105 0.8 3. Impranil ®ELH 7200 300 120.2 125 0.9 4. Ru ®41-710 7000 600 27.3 26.4 0.8 5. Ru ® 40-350 7000 500 34.4 36.2 0.8 6.Bayhydrol ® 6000 300 8.6 5.7 0.8 123 7. Dow Corning 700 90 <2 <2 2.13625** 8. Silastic 94-595- 1400 580 <2 <2 1.8 HC** 9. Ru ® 40-415 5000180 <2 <2 0.8 10. Sancure ® 861 3000 580 25.2 <2 0.8 11. Witcobond ®6000 600 28.4 <2 0.8 290H *Aging conditions: 107° C. oven aging for 16days, followed by 83° C. and 95% relative humidity aging for 16 days.**The resins are silicone rubbers.

As noted above, Examples 1-6 work extremely well and are thus within thescope of this invention. Examples 10 and 11 show some limitations,polyester based elastomers (Witcobond® 290H) exhibit excellent heataging (oxidation) stability but tend to hydrolyze easily at highhumidity; polyether based elastomers (Sancure® 861) have excellenthydrolysis resistance, but poor oxidation performance. However, theseelastomers have proven to be acceptable permeability reducers at higheradd-on weights below the maximum of 3.0 ounces per square yard.Furthermore, although silicones show excellent resistance to heat agingand hydrolysis (humidity aging), they, however, possess limited tensilestrength and tear resistance resistance. Natural rubber, SBR chloroprenerubbers and others containing unsaturated carbon double bonds haveexcellent hydrolysis resistance. But the unsaturated carbon double bondthat gives their elasticity oxidizes readily and the properties of therubber change after heat aging. Elastomers that have good physicalproperties and excellent resistance to hydrolysis and oxidation arepreferred for this application. Polyurethanes based on polycarbonatesoft segments are the preferred materials for this application.

The airbag of Example 3 exhibited a sliding coefficient of frictionconstant of roughly 0.6. A comparative thick silicone-coated sidecurtain airbag which included a non-woven layer, exhibited a constant ofabout 0.8.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an inventive all-woven inflatablefabric showing the preferred double and single layer area including twoseparate single layer areas.

FIG. 2 is a weave diagram illustrating a potentially preferred repeatingpick pattern formed using repeating plain weave and basket weavefour-pick arrangements.

FIG. 3 depicts the side, inside view of a vehicle prior to deployment ofthe inventive side curtain airbag.

FIG. 4 depicts the side, inside view of a vehicle after deployment ofthe inventive side curtain airbag.

FIG. 5 depicts a side view of a side curtain airbag.

FIG. 6 provides a side view of a side curtain airbag container.

FIG. 7 provides a cross-sectional perspective of the stored airbagwithin the container of FIG. 6.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now to the drawings, in FIG. 1 there is shown a cross-section ofa preferred structure for the double fabric layers 12, 14, 18, 20, 24,26 and single fabric layers 16, 22 of the inventive inflatable fabric10. Weft yarns 28 are present in each of these fabric layer areas 12,14, 16, 18, 20, 22, 24, 26 over and under which individual warp yarns38, 40, 42, 44 have been woven. The double fabric layers 12, 14, 18, 20,24, 26 are woven in plain weave patterns. The single fabric layers 16,22 are woven in basket weave patterns. Four weft yarns each areconfigured through each repeating basket weave pattern within thispreferred structure; however, anywhere from two to twelve weft yarns maybe utilized within these single fabric layer areas (seams) 16, 22. Theintermediate double fabric layer areas 18, 20 comprise each only fourweft yarns 28 within plain weave patterns. The number of suchintermediate weft yarns 28 between the single fabric layer areas 16, 22must be in multiples of two to provide the maximum pressure bearingbenefits within the two seams 16, 22 and thus the lowest possibility ofyarn shifting during inflation at the interfaces of the seams 16, 22with the double fabric layer areas 12, 14, 24, 26.

FIG. 2 shows the weave diagram 30 for an inventive fabric whichcomprises two irregularly shapes concentric circles as the seams. Such adiagram also provides a general explanation as to the necessaryselection criteria of placement of basket-weave patterns within thefabric itself Three different types of patterns are noted on the diagramby different shades. The first 32 indicates the repeated plain weavepattern throughout the double fabric layers (12, 14, 18, 20, 24, 26 ofFIG. 1, for example) which must always initiate at a location in thewarp direction of 4X+1, with X representing the number of pickarrangement within the diagram, and at a location in the fill directionof 4X+1 (thus, the pick arrangement including the specific two-layerplain-weave-signifying-block 32 begins at the block four spaces below itin both directions). The second 34 indicates an “up-down” basket weavepattern wherein an empty block must exist and always initiate thebasket-weave pattern at a location in the warp direction of 4X+1, with Xrepresenting the number of repeating pick arrangements within thediagram, and at a location in the fill direction of 4X+1, when a seam(such as 16 and 22 in FIG. 1) is desired (thus, the pattern includingthe pertinent signifying “up-down” block 34 includes an empty blockwithin the basket-weave pick arrangement in both the warp and filldirections four spaces below it). The remaining pattern, which isbasically a “down-up” basket weave pattern to a single fabric layer(such as 16 and 22 in FIG. 1) is indicated by a specifically shadedblock 36. Such a pattern must always initiate at a location in the warpdirection of 4X+1 and fill of 4X+3, or warp of 4X+3 and fill of 4X+1,when a seam is desired. Such a specific arrangement of differing“up-down” basket weave 34 and “down-up” basket weave 36 pattern isnecessary to effectuate the continuous and repeated weave constructionwherein no more than three floats (i.e., empty blocks) are presentsimultaneously within the target fabric structure. Furthermore, again,it is believed that there has been no such disclosure or exploration ofsuch a concept within the inflatable fabric art.

As depicted in FIG. 3, an interior of a vehicle 110 prior to inflationof a side curtain airbag (not illustrated) is shown. The vehicle 110includes a front seat 112 and a back seat 114, a front side window 116and a back-side window 118, a roofline 120, within which is stored acylindrically shaped container 122 comprising the inventive side curtainairbag (not illustrated). Also present within the roofline 120 is aninflator assembly 124 which ignites and forces gas into the side curtainairbag (126 of FIG. 4) upon a collision event.

FIG. 4 shows the inflated side curtain airbag 126. As noted above, theairbag 126 is coated with at most 2.5 ounces per square of a coatingformulation (not illustrated), preferably polyurethane polycarbonate.The inventive airbag 126 will remain sufficiently inflated for at least5 seconds, and preferably more, as high as at least 20 seconds, mostpreferably.

FIG. 5 shows the side curtain airbag 126 prior to storage in itsuninflated state within the roofline cylindrically shaped container 122.The thickness of the airbag 126, measured as the rolled packing diameter(as in FIG. 7, below) as compared with the depth of the airbag measuredfrom the roofline cylindrically shaped container 122 to the bottom mostpoint 128 of the airbag 126 either in its uninflated or inflated statewill be at least 17 and at most 29, as noted above.

FIGS. 6 and 7 aid in understanding this concept tough the viewing of therolled airbag 126 as stored within the container 122 along line 2. Thediameter measurement of the airbag 126 of Example 3, above, is roughly20 millimeters. The standard depth of side curtain airbags is roughly 17inches or about 431.8 millimeters. Thus, the preferred packing volumefactor is about 21.6. A comparative silicone-based thick coating add-onweight of about 4.0 ounces per square yard provided a diameter of about25 millimeters for a factor of about 17.3.

There are, of course, many alternative embodiments and modifications ofthe present invention which are intended to be included within thespirit and scope of the following claims.

What is claimed is:
 1. A one-piece woven airbag cushion comprising acoated inflatable fabric, wherein said inflatable fabric is at leastpartially coated with an elastomeric composition; wherein said airbagcushion exhibits a characteristic leak-down time after inflation of atleast 5 seconds; wherein said inflatable fabric comprises at least twolayers of fabric in certain discrete areas of the fabric and at leastone narrow single fabric layer at a discrete area within said fabric;wherein said at least one narrow single fabric layer is the sole sourceof providing inflatable pillow structures within said airbag cushion;and wherein said at least one narrow single fabric layer is formedsolely from a basket weave pattern of an even number of yarns, at most12 yarns in width.
 2. The airbag cushion of claim 1 wherein saidelastomeric composition is present on the surface of said inflatablefabric in an amount of at most 3.0 ounces per square yard of the fabric.3. The fabric of claim 2 wherein the weave pattern of said at least twolayers of fabric within said inflatable fabric is a plain weave pattern.4. The airbag cushion of claim 2 wherein said elastomeric composition iscosted on said inflatable fabric surface in an amount of at most 2.0ounces per square yard.
 5. The airbag cushion of claim 4 wherein saidelastomeric composition is coated on said airbag fabric surface in anamount 1.5 ounces per square yard.
 6. The airbag cushion of claim 5wherein said elastomeric composition is coated on said airbag fabricsurface in an amount of at most 1.2 ounces per square yard.
 7. Theairbag cushion of claim 6 wherein said elastomeric composition is coatedon said airbag fabric surface in an amount at most 1.0 ounces per squareyard.
 8. The airbag cushion of claim 7 wherein said elastomericcomposition is coated on said airbag fabric surface in an amount of atmost 0.8 ounces per square yard.
 9. The fabric of claim 1 wherein saidat least two layers of fabric within said inflatable fabric are formedsolely from one type of weave pattern, wherein said weave pattern is nota basket weave pattern.
 10. The fabric of claim 1 wherein at least twodiscrete narrow areas of single fabric layers are present within saidinflatable fabric, wherein said at least two single fabric layers areseparated by an area of two layers of fabric, and wherein the lengths ofeach single layer is from 4 to 8 yarns in length.
 11. The fabric ofclaim 10 wherein said at least two single fabric layer areas areconstructed solely from basket weave patterns containing at least twoyarns per basket pattern and at most four yarns per basket pattern. 12.The fabric of claim 11 said separator two layers of fabric between saidtwo single layers of fabric comprises an even number of weft yarns. 13.The fabric of claim 12 wherein said separator two layers of fabriccomprises at most 12 weft yarns and at least 2 weft yarns.
 14. Thefabric of claim 13 wherein said at least two single fabric layers areconstructed solely from two-by-two basket weave patterns and saidseparator double fabric layer comprises four weft yarns.
 15. The airbagcushion of claim 1 wherein said elastomeric composition comprises atleast one elastomer exhibiting a tensile strength of at least 2,000 psiand an elongation at break of at least 180%.
 16. The airbag cushion ofclaim 15 wherein said elastomeric composition is present in the form ofa resin solution in an organic solvent.
 17. The airbag cushion of claim1 wherein said elastomeric composition comprises polyurethane.
 18. Theairbag cushion of claim 17, wherein said elastomeric polyurethanecomposition is polycarbonate polyurethane.
 19. The airbag cushion ofclaim 1 wherein said coated fabric is woven from polyamide yarns. 20.The airbag cushion of claim 19 wherein said polyamide yarns are formedfrom nylon 6,6 fiber.
 21. The airbag cushion of claim 19, wherein saidpolyamide yarns are multifilament yarns exhibiting a linear density ofabout 210-840 denier.
 22. The airbag cushion of claim 21, wherein saidmultifilament yarns exhibit a filament linear density of about 4 denierper filament or less.
 23. A one-piece woven airbag cushion comprising acoated inflatable fabric, wherein said inflatable fabric is at leastpartially coated with an elastomeric composition; wherein said airbagcushion exhibits a characteristic leak-down time after inflation of atleast 5 seconds; wherein said inflatable fabric comprises at least twolayers of fabric in certain discrete areas of the fabric and at leastone single fabric layer at a discrete area within said fabric; whereinsaid at least one narrow single fabric layer is the sole source ofproviding inflatable pillow structures within said airbag cushion;wherein said at least one narrow single fabric layer is solely formedfrom a weave pattern of at most 12 yarns in width; and wherein the weavediagram for such an inflatable fabric does not exhibit more than threeconsecutive unfilled blocks in any row or column.
 24. The airbag cushionof claim 23 wherein said elastomeric composition is present on thesurface of said inflatable fabric in an amount of at most 3.0 ounces persquare yard of the fabric.
 25. The airbag cushion of claim 24 whereinsaid elastomeric composition is coated on said airbag fabric surface inan amount of at most 2.0 ounces per square yard.
 26. The airbag cushionof claim 25 wherein said elastomeric composition is coated on saidairbag fabric surface in an amount of at most 1.5 ounces per squareyard.
 27. The airbag cushion of claim 26 wherein said elastomericcomposition is coated on said airbag fabric surface in an amount of atmost 1.2 ounces per square yard.
 28. The airbag cushion of claim 27wherein said elastomeric composition is coated on said airbag fabricsurface in an amount of at most 1.0 ounces per square yard.
 29. Theairbag cushion of claim 28 wherein said elastomeric composition iscoated on said airbag fabric surface in an amount of at most 0.8 ouncesper square yard.
 30. The airbag cushion of claim 23 wherein wherein saidelastomeric composition comprises at least one elastomer exhibiting atensile strength of at least 2,000 psi and an elongation at break of atleast 180%.
 31. The airbag cushion of claim 30, wherein said elastomericcomposition is present in the form of a resin solution in an organicsolvent.
 32. The airbag cushion of claim 23 wherein said elastomericcomposition comprises polyurethane.
 33. The airbag cushion of claim 32,wherein said elastomeric polyurethane composition is polycarbonatepolyurethane.
 34. The airbag cushion of claim 23 wherein said coatedfabric is woven from polyamide yarns.
 35. The airbag cushion of claim 34wherein said polyamide yarns are formed from nylon 6,6 fiber.
 36. Theairbag cushion of claim 35, wherein said multifilament yarns exhibit afilament linear density of about 4 denier per filament or less.
 37. Theairbag cushion of claim 34, wherein said polyamide yarns aremultifilament yarns exhibiting a linear density of about 210-630 denier.38. A one-piece woven airbag cushion comprising a coated inflatablefabric, wherein said inflatable fabric is at least partially coated withan elastomeric composition; wherein said airbag cushion exhibits acharacteristic leak-down time after inflation of at least 5 seconds;wherein said inflatable fabric comprises at least two layers of fabricin certain discrete areas of the fabric and at least one narrow singlefabric layer at a discrete area within said fabric; wherein said atleast one narrow single fabric layer is the sole source of providinginflatable pillow structures within said airbag cushion; wherein said atleast one narrow single fabric layer is solely formed from a weavepattern of at most 12 yarns in width; and wherein only two separateweave densities are present within the area directly adjacent to said atleast one narrow single fabric layer.
 39. The airbag cushion of claim 38wherein said elastomeric composition is present on the surface of saidinflatable fabric in an amount of at most 3.0 ounces per square yard ofthe fabric.
 40. The airbag cushion of claim 39 wherein said elastomericcomposition is coated on said airbag fabric surface in an amount of atmost 2.0 ounces per square yard.
 41. The airbag cushion of claim 39wherein said elastomeric composition is coated on said airbag fabricsurface in an amount of at most 1.5 ounces per square yard.
 42. Theairbag cushion of claim 41 wherein said elastomeric composition iscoated on said airbag fabric surface in an amount of at most 1.2 ouncesper square yard.
 43. The airbag cushion of claim 42 wherein saidelastomeric composition is coated on said airbag fabric surface in anamount of at most 1.0 ounces per square yard.
 44. The airbag cushion ofclaim 43 wherein said elastomeric composition is coated on said airbagfabric surface in an amount of at most 0.8 ounces per square yard. 45.The airbag cushion of claim 38 wherein said elastomeric compositioncomprises at least one elastomer exhibiting a tensile strength of atleast 2,000 psi and an elongation at break of at least 180%.
 46. Theairbag cushion of claim 45, wherein said elastomeric composition ispresent in the form of a resin solution in an organic solvent.
 47. Theairbag cushion of claim 38 wherein said elastomeric compositioncomprises polyurethane.
 48. The airbag cushion of claim 47, wherein saidelastomeric polyurethane composition is polycarbonate polyurethane. 49.The airbag cushion of claim 38 wherein said coated fabric is woven frompolyamide yarns.
 50. The airbag cushion of claim 38 wherein saidpolyamide yarns are formed from nylon 6,6 fiber.
 51. The airbag cushionof claim 50, wherein said polyamide yarns are multifilament yarnsexhibiting a linear density of about 210-630 denier.
 52. The airbagcushion of claim 51, wherein said multifilament yarns exhibit a filamentlinear density of about 4 denier per filament or less.
 53. A one-piecewoven airbag cushion comprising a coated inflatable fabric, wherein saidinflatable fabric is at least partially coated with an elastomericcomposition; wherein said airbag cushion exhibits a characteristicleak-down time after inflation of at least 5 seconds; wherein saidinflatable fabric comprises at least two layers of fabric in certaindiscrete areas of the fabric and a plurality of narrow single fabriclayers in at least two discrete areas within said fabric; wherein saidat least two narrow single fabric layers are the sole source ofproviding inflatable pillow structures within said airbag cushion; andwherein the narrow single fabric layers present within said two discreteareas within said fabric are formed solely from a basket weave patternof an even number of yarns, from 4 to 8 yarns in width.
 54. The airbagcushion of claim 53 wherein said elastomeric composition is present onthe surface of said inflatable fabric in amount of at most 3.0 ouncesper square yard of the fabric.
 55. The airbag cushion of claim 54wherein said elastomeric composition is coated on said airbag fabricsurface in an amount of at most 2.0 ounces per square yard.
 56. Theairbag cushion of claim 55 wherein said elastomeric composition iscoated on said airbag fabric surface in an amount of at most 1.5 ouncesper square yard.
 57. The airbag cushion of claim 56 wherein saidelastomeric composition is coated on said airbag fabric surface in anamount of at most 1.2 ounces per square yard.
 58. The airbag cushion ofclaim 57 wherein said elastomeric composition is coated on said airbagfabric surface in an amount of at most 1.0 ounces per square yard. 59.The airbag cushion of claim 58 wherein said elastomeric composition iscoated on said airbag fabric surface in an amount of at most 0.8 ouncesper square yard.
 60. The airbag cushion of claim 53 wherein saidelastomeric composition comprises at least one elastomer exhibiting atensile strength of at least 2,000 psi and an elongation at break of atleast 180%.
 61. The airbag cushion of claim 60, wherein said elastomericcomposition is present in the form of a resin solution in an organicsolvent.
 62. The airbag cushion of claim 53 wherein said elastomericcomposition comprises polyurethane.
 63. The airbag cushion of claim 62,wherein said elastomeric polyurethane composition is polycarbonatepolyurethane.
 64. The airbag cushion of claim 53 wherein said coatedfabric is woven from polyamide yarns.
 65. The airbag cushion of claim 64wherein said said yarns are formed from nylon 6,6 fiber.
 66. The airbagcushion of claim 65, wherein said polyamide yarns are multifilamentyarns exhibiting a linear density of about 210-630 denier.
 67. Theairbag cushion of claim 66, wherein said multifilament yarns exhibit afilament linear density of about 4 denier per filament or less.
 68. Acoated side curtain airbag exhibiting a rolled packing volume factor offrom about 17 to about 24; wherein said coated side curtain airbagexhibits a leak-down time after inflation of at least 7 seconds; andwherein said inflatable fabric comprises at least two layers of fabricin certain discrete areas of the fabric and at least one narrow singlefabric layer at a discrete area within said fabric; wherein said atleast one narrow single fabric layer is the sole source of providinginflatable pillow structure within said airbag cushion; and wherein saidat least one narrow single fabric layer is formed solely from a basketweave pattern of an even number of yarns, at most 12 yarns in width. 69.The airbag cushion of claim 68 wherein said rolled packing volume factoris about 21.6.